1. Field of the Invention
The present invention relates to orthopedic implants and, more particularly, to foldable orthopedic implants such as are used in minimally invasive surgery of which a spinal implant is a type.
2. Background Information
There are situations in orthopedic surgeries when it would be desirable to have an implant that would be self-deployable. One such orthopedic situation is with relation to the spine as related below.
The disc between vertebrae of a human spine may sometimes become damaged due to disease or injury, or may simply deteriorate due to age, defect or the like. With others, the vertebrae may become compressed or otherwise damaged for various reasons. In these and other cases the vertebrae can become too closely spaced anteriorly which causes an undesired abnormal curvature of the spine with respect to lordosis or kyphosis.
Because of this, surgery may be utilized to place one or more spinal spacers or interbody devices between adjacent vertebrae in order to provide proper spacing and/or orientation of the vertebrae. In some cases the spinal interbody device may be an artificial or prosthetic spinal disc that is designed to replace the existing spinal disc. In some cases the spinal interbody device is a device that supports and/or realigns the adjacent vertebrae relative to one another and which promotes fusion between the vertebrae. Bone fusion material is typically used with spinal implant devices in order to promote growth of the bone between the adjacent vertebrae to thereby create fusion of the adjacent vertebrae. The bone fusion material is placed about or in the spinal implant device.
When spinal interbody devices are used, it is desirable for them to engage as much surface of the bone of the vertebrae as possible to provide support to the bone and to thereby reduce the likelihood of subsidence of the device into the vertebrae or bone resulting from contact pressure of the spinal interbody device against bone surfaces. Subsidence can occur since part of the bone is somewhat spongy in nature, especially near the centers of the adjacent vertebrae.
The configuration and/or structure of spinal interbody devices functions to provide support, spacing and orientation between the two adjacent vertebrae. Therefore, one or more dimensions of the implant device, such as height or intervertebral spacing (i.e. the distance between an upper vertebral surface of a lower vertebra of the vertebrae pair to a lower vertebral surface of an upper vertebra of the vertebrae pair), must correspond to a desired intervertebral spacing. This dimension may be relatively large. Since it is desirable to employ minimally invasive surgical procedures (minimally invasive surgery or MIS) when possible, the user of spinal implant, spinal implant devices of certain sizes cannot be used. Therefore, spinal implant devices have been developed that are small enough to be implanted using MIS and which can then be expanded after implantation. These devices, however, require the surgeon to mechanically expand the implant device once implanted. This is not easy when using MIS. Mechanically expandable spinal implant devices are also deficient in other areas.
Accordingly, there presently exists a need for improved spinal implants, particularly for MIS use. Moreover, there presently exists a need for improved orthopedic implants in general.